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471.
The arctic tundra ponds at the International Biological Program (IBP) site in Barrow, AK, were studied extensively in the
1970s; however, very little aquatic research has been conducted there for over three decades. Due to the rapid climate changes
already occurring in northern Alaska, identifying any changes in the ponds’ structure and function over the past 30–40 years
can help identify any potential climate-related impacts. Current research on the IBP ponds has revealed significant changes
in the physical, chemical, and biological characteristics of these ponds over time. These changes include increased water
temperatures, increased water column nutrient concentrations, the presence of at least one new chironomid species, and increased
macrophyte cover. However, we have also observed significant annual variation in many measured variables and caution that
this variation must be taken into account when attempting to make statements about longer-term change. The Barrow IBP tundra
ponds represent one of the very few locations in the Arctic where long-term data are available on freshwater ecosystem structure
and function. Continued monitoring and protection of these invaluable sites is required to help understand the implications
of climate change on freshwater ecosystems in the Arctic. 相似文献
472.
中国农田生态系统碳净吸收重心移动及其原因 总被引:1,自引:0,他引:1
为深入了解我国农田生态系统碳净吸收的区域差异及其原因,本文采用重心模型分析了农田系统碳净吸收重心移动规律,运用C-D生产函数分析了影晌农田系统碳净吸收重心移动的因素,并在此基础上计算了各影响因素对各区域碳净吸收的贡献率,提出了相应的政策建议.结果表明:①我国农田系统碳净吸收重心坐标经度减小较快,纬度波动增加,落实到地理区域上呈向西北方向移动的趋势.东南区与蒙新区是农田系统碳净吸收比重下降和增长速度最快的地区,而西南区已逐渐成为我国农田系统碳净吸收的主要贡献区.②常规投入中土地投入是影响农田系统碳净吸收重心移动的首要因素,资本投入(包括化肥、劳动力)也是重要的影响因素:控制变量中种植结构是主要影响因素,使用权与收益权变量系数显著但影响不大.③各影响因素对区域碳净吸收的贡献存在显著的地区差异,但影响各区域碳净吸收的主要贡献因素为土地、化肥和种植结构. 相似文献
473.
474.
Capturing the lost phosphorus 总被引:4,自引:0,他引:4
Minable phosphorus (P) reserves are being depleted and will need to be replaced by recovering P that currently is lost from the agricultural system, causing water-quality problems. The largest two flows of lost P are in agricultural runoff and erosion (∼46% of mined P globally) and animal wastes (∼40%). These flows are quite distinct. Runoff has a very high volumetric flow rate, but a low P concentration; animal wastes have low flow rates, but a high P concentration together with a high concentration of organic material. Recovering the lost P in animal wastes is technically and economically more tractable, and it is the focus for this review of promising P-capture technologies. P capture requires that organic P be transformed into inorganic P (phosphate). For high-strength animal wastes, P release can be accomplished in tandem with anaerobic treatment that converts the energy value in the organic matter to CH4, H2, or electricity. Once present as phosphate, the P can be captured in a reusable form by four approaches. Most well developed is precipitation as magnesium or calcium solids. Less developed, but promising are adsorption to iron-based adsorbents, ion exchange to phosphate-selective solids, and uptake by photosynthetic microorganisms or P-selective proteins. 相似文献
475.
476.
Plant uptake of pesticides and human health: dynamic modeling of residues in wheat and ingestion intake 总被引:2,自引:0,他引:2
Human intake of pesticide residues from consumption of processed food plays an important role for evaluating current agricultural practice. We take advantage of latest developments in crop-specific plant uptake modeling and propose an innovative dynamic model to estimate pesticide residues in the wheat-environment system, dynamiCROP. We used this model to analyze uptake and translocation of pesticides in wheat after foliar spray application and subsequent intake fractions by humans. Based on the evolution of residues in edible parts of harvested wheat we predict that between 22 mg and 2.1 g per kg applied pesticide are taken in by humans via consumption of processed wheat products. Model results were compared with experimentally derived concentrations in wheat ears and with estimated intake via inhalation and ingestion caused by indirect emissions, i.e. the amount lost to the environment during pesticide application. Modeled and measured concentrations in wheat fitted very well and deviate from less than a factor 1.5 for chlorothalonil to a maximum factor 3 for tebuconazole. Main aspects influencing pesticide fate behavior are degradation half-life in plant and time between pesticide application and crop harvest, leading to variations in harvest fraction of at least three orders of magnitude. Food processing may further reduce residues by approximately 63%. Intake fractions from residues in sprayed wheat were up to four orders of magnitude higher than intake fractions estimated from indirect emissions, thereby demonstrating the importance of exposure from consumption of food crops after direct pesticide treatment. 相似文献
477.
478.
选择4种常见的湿地植物,研究了重金属锌胁迫下,湿地植物对磷的吸收能力的变化。结果表明,当加入0.5 g ZnSO4/kg 土壤时,4种湿地植物根表铁氧化物胶膜对锌的吸附量增加,而对磷的吸附量显著降低(p<0.05);湿地植物根表铁氧化物胶膜上吸附的磷是湿地植物吸收的磷源,并影响湿地植物地上部分磷含量;在高浓度锌的胁迫下,灯心草地上部分铁含量增加,而导致地上部分磷含量显著降低(p<0.05)。湿地植物根表铁氧化物胶膜上的锌和地上部分铁含量都影响了湿地植物对磷的吸收。 相似文献
479.
Doris Vetterlein Dirk Wesenberg Petra Nathan Anja Brutigam Angelika Schierhorn Jürgen Mattusch Reinhold Jahn 《Environmental pollution (Barking, Essex : 1987)》2009,157(11):3016-3024
Pteris vittata is known to hyperaccumulate As but the mechanism is poorly understood. We found an increase of As concentration with increasing soil solution As concentrations, but P application had no impact, although plant P concentrations responded to different rates of P supply. As in fronds was dominantly (82–89%) present in the form of AsIII. In roots we detected 45% as AsIII which is higher than reported in previous studies and supports substantial As-reduction to take place in roots. We detected PC2/3GS–AsIII, PC2–GS–AsIII and (PC2)2–AsIII in increasing amounts with application of As. The total amount of PC was in the range reported previously and far too small to assign a significant role in As detoxification to PCs. The close correlation between S and As in fronds and the lack of data on sulphur uptake and metabolism indicates the need for a detailed investigation on sulphur nutritional status and As metabolism in P. vittata. 相似文献
480.
Reuse of mining wastewater in agricultural activities in Jordan 总被引:1,自引:0,他引:1
Omar Rimawi Anwar Jiries Yasin Zubi Ali El-Naqa 《Environment, Development and Sustainability》2009,11(4):695-703
A pilot study was completed in the Al-Abyad area near phosphate mining activity in Jordan. Six plots of 50 m2 each were planted with two types of plant species (Zea mays spp. and Medicago lupulina spp.) and irrigated using three types of water (fresh groundwater, mine wastewater, and hydride water consisting of 50% fresh
and 50% mine wastewater) to investigate the suitability of utilizing mine wastewater for food production in the area. Water,
soil and plant sampling was completed for each plot over different time intervals and analyzed for heavy metal (Cr+6, Ni+2, Zn+2 and Pb+2) in addition to major ionic composition of the water used for irrigation. Crop yield was estimated at the end of the experiment.
Plots irrigated with mine wastewater showed slightly higher heavy metals concentrations and soil salinity during the experiment
period was higher for plots irrigated with mine wastewater compared to plots irrigated with fresh water, and it was uniform
through the upper 45 cm of the soil profile due to the high amount of irrigation water used during the experiment. Crop yield
was inversely proportional to salinity as an increase of salinity by 2-folds resulted in reducing yield by almost 50%. However,
no risk of heavy metals contamination was found in plants and soil.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献